Background
Prospective multicenter study (German Cooperative Group on Radiotherapy for Benign Diseases). 318 patients undergoing THA or acetabular fracture repair at high risk for HO formation. Evaluated single-fraction postoperative RT vs short-course (3–6 Gy × 3–4 fractions) for HO prophylaxis. Aimed to determine optimal RT dose and fractionation for preventing clinically significant HO. Seegenschmiedt MH et al, IJROBP 2001.
Interventions and follow up
Arm A: Single fraction RT: 7 Gy × 1 within 72 hours post-surgery
Arm B: Short-course RT: 3 Gy × 4 fractions (12 Gy total) over 1 week post-surgery
Primary endpoint: HO rate (Brooker classification) at 6 and 12 month
mFollow up: 12 month
Arm B: Short-course RT: 3 Gy × 4 fractions (12 Gy total) over 1 week post-surgery
Primary endpoint: HO rate (Brooker classification) at 6 and 12 month
mFollow up: 12 month
Results
High-risk criteria: Prior HO, DISH, ankylosing spondylitis, hypertrophic osteoarthritis, male sex, bilateral THA
Any HO (single fraction 7 Gy): 28% vs short course 30% — equivalent
Severe HO (Brooker III–IV): 5% (7 Gy) vs 7% (12 Gy), P=.42 — not significant
RT preoperative (same day): Equivalent to postoperative (24 hr delay)
Any HO (single fraction 7 Gy): 28% vs short course 30% — equivalent
Severe HO (Brooker III–IV): 5% (7 Gy) vs 7% (12 Gy), P=.42 — not significant
RT preoperative (same day): Equivalent to postoperative (24 hr delay)
Adverse events
Main adverse events: Both arms: acute skin erythema grade 1 (35%), mild hip discomfort 24 hours post-RT in 15%. No wound healing complications attributable to RT. No secondary malignancies at 12-month follow-up. Preoperative RT has theoretical advantage of avoiding post-surgical edema affecting field setup.
Conclusions
Single-fraction 7 Gy is equivalent to 12 Gy/4 fractions for HO prophylaxis after THA. Single-fraction is preferred for patient convenience and equivalent efficacy. RT may be delivered preoperatively (same day) or postoperatively (within 72 hours) with equivalent results.
Key Limitations
Key Limitations: No randomized control vs observation or NSAIDs. Short follow-up (12 months) — some HO may develop later. Risk stratification for "high-risk" HO not standardized. Preoperative RT exposes normal tissue before surgical trauma and may theoretically impair healing — though this was not observed in this study.
Clinical Context
Single-fraction RT 7 Gy (within 24–72 hours post-THA) is the established standard. Some centers deliver RT preoperatively (within 4 hours before surgery) for logistical convenience. RT fields should include the peritrochanteric region and femoral neck/acetabulum. Testicular/ovarian shielding is mandatory. RT is most commonly used for high-risk patients when NSAIDs are contraindicated.
References